SNPA Strapline


Oak Woodland

alt=Torrent Walk, Brithdir, Dolgellau

Biosecurity - Tree Diseases

Both native and introduced trees in Wales are potentially susceptible to a wide range of pests and pathogens, as well as abiotic sources of damage such as extreme weather and pollution.

Trees can support populations of many insects and fungi without suffering serious damage. From time to time population explosions, unusual weather conditions or the introduction of a new pest can lead to trees being badly damaged or even killed. Outbreaks of pests and diseases which affect large numbers of trees can have significant effects on our landscapes, natural habitats and economy.

In the last few years, the outbreaks of Phytophthora ramorum and Chalara dieback of ash (Chalara fraxinea) have raised the profile of tree diseases in the UK. Acute oak decline has also been confirmed on oaks in Wales.

Phytophthora ramorum is a fungal disease spread by both water and in the air that can affect a variety of plants. Its main hosts are rhododendron and larch but it can also attack other tree species as well as garden plants such as viburnum and magnolia and heathland plants such as bilberry.

Chalara fraxinea more commonly known as ash dieback is a fungal disease specific to ash. It is dispersed by wind borne spores.

Phytophthora ramorum (© SNPA)

Phytophthora ramorum (© SNPA)

Trees at Dysefin farm (© SNPA)

Trees at Dysefin farm (© SNPA)

How can you help?

  • Please keep to marked paths in woodlands - This helps reduce the chances of picking up contaminated soil and plant debris on footwear.
  • Pay attention to site notices - Infected areas may be signed or cordoned off.
  • Clean your footwear - Remove soil and plant debris from your shoes or boots after each visit.
  • Clean the tires of bikes and vehicles - If you’ve been off road, remove soil and plant debris from your tires.
  • Don’t take plants or cuttings - Taking plants home risks introducing the infection to your own garden.
  • Report sightings of infected trees - Contact the National Park if you come across infected woodlands